Little Ice Age subject of study

BOULDER, Colo., Jan. 30 (UPI) -- A Little Ice Age from the Middle Ages into the late 19th century had a volcanic beginning that affected sea ice in the North Atlantic, U.S. researchers say.

A study led by the University of Colorado Boulder suggests the Little Ice Age began abruptly between A.D.1275 and 1300, triggered by repeated, explosive volcanism and sustained by a self- perpetuating sea ice-ocean feedback system in the North Atlantic Ocean.

Researcher Gifford Miller said the study analyzed radiocarbon dates from dead vegetation emerging from rapidly melting icecaps on Baffin Island in the Canadian Arctic, along with ice and sediment core data from the poles and Iceland and from sea ice climate model simulations.

The data suggest an unusual, 50-year-long episode of four massive tropical volcanic eruptions kicked off the cooling of Earth, and the persistence of cold summers following the eruptions was created by the weather feedback system of melting ice and cooler waters in the North Atlantic Ocean, a UC Boulder release said Monday.

"The eruptions could have triggered a chain reaction, affecting sea ice and ocean currents in a way that lowered temperatures for centuries," said researcher Bette Otto-Bliesner of the National Center for Atmospheric Research in Boulder.